1. Field of the Invention
This invention relates to a World Wide Web-based melody retrieval system, and more particularly to a World Wide Web-based melody retrieval system with thresholds determined by using distribution of pitch and span of notes from a music database.
2. Description of the Prior Art
It should be understood that the problem in building a melody retrieval system is that an input melody includes various errors which are caused by the uncertainty of the user's memory or by the user's singing ability. Those errors are usually tolerated by using several thresholds and converting the input melody into approximate relative-value sequences of pitch change (the pitch difference between adjacent notes) and of span change (the inter-onset interval ratio of adjacent notes).
For instance, an approximate relative-pitch value is expressed by using three characters (U(p), D(own), and E(qual)), and the sequence "do-re-mi-mi-re-do" is converted into "X-U-U-E-D-D-" (wherein "X" indicates the first not which does not have a relative value). These approximate sequences are then utilized in the matching process which compares the input with all songs in a database.
Prior melody retrieval systems [Kageyama et al. 1993; Ghias et al. 1995] utilized the static heu-ristic thresholds to obtain these approximate sequences. Since it is difficult to determine the optimum thresholds for all songs, those systems did not take advantage of the span information which can potentially be useful, and mainly used pitch information as a search clue.
It was therefore difficult to improve the matching accuracy by using only the pitch information.
It was also difficult to reduce the number of answer candidates because several songs in the large database tended to have the same patterns of the approximate relative-values of pitch and span sequences.
Moreover, the public use of music database over the network has not been considered.
In the conventional music retrieval systems, the pitch information is mainly used as a search clue while the span information is not used effectively, and it is difficult to improve the matching accuracy by using only the pitch information.